Graft polymers based on polyalkylene oxides and vinyl esters, in particular vinyl acetate, are known from DE-B-1 077 430 and GB-B-922 457. They are prepared by polymerizing the vinyl ester in the presence of the polyalkylene oxide, the initiator used being dibenzoyl peroxide, dilauroyl peroxide or diacetyl peroxide. In the examples of these documents, the procedure is to prepare a solution from all reactants. This solution is either heated directly to the polymerization temperature or only a portion is initially charged and heated or the majority is metered in. In the first variant, it is also possible for larger amounts of solvent such a methyl acetate or methanol to be present (100% or 72% based on the amount of polyalkylene glycol and vinyl ester). Further procedures are merely mentioned in GB-B-922 457 but not used in the examples for preparing the graft polymers.
According to EP-A-219 048 and EP-285 037, graft polymers based on polyalkylene oxides and vinyl esters are suitable as graying inhibitors in the washing and after treatment of textiles comprising synthetic fibers. For this purpose, EP-A-285 935 and EP-285 038 also recommend graft polymers which comprise methyl acrylate or N-vinylpyrrolidone in copolymerized form as an additional graft monomer. For the preparation of the graft polymers used in the examples, no specific data are given and reference is made merely in general terms to DE-B-1 077 430 and GB-B-922 457.
The document WO 2009/013202 A1 describes a process for preparing copolymers in solid form wherein the copolymers are obtained by free-radically initiated polymerization of a mixture of 30 to 80% by weight of N-vinyllactam, 10 to 50% by weight of the vinyl acetate and 10 to 50% by weight of a polyether, in the presence of at least one solvent, with the proviso that the sum is 100% by weight, characterized in that the solvents are removed from the polymerization mixture with the aid of an extruder.
The document WO 2007/138054 A1 relates to laundry detergents and cleaning compositions comprising amphiphilic graft polymers based on water-soluble polyalkylene oxides (A) as a graft base and side chains formed by polymerization of a vinyl ester component (B), said polymers having an average of ≦1 graft site per 50 alkylene oxide units and mean molar masses Mw of from 3,000 to 100,000 g/mol. The invention further relates to the use of these amphiphilic graft polymers as a soil detachment/promoting additive to laundry detergents and cleaning compositions.
The document DE 10 2006 055 473 A1 describes a process for the preparation of graft polymers on the basis of polyethers and vinyl esters by conversion of polyethers, vinyl ester and further hydrophobic monomers in the presence of an organic solvent and a radical forming polymerization initiator under reflux conditions.
The document WO 2011/054789 A1 relates to a method for producing aqueous solutions of homo or copolymers of acrylic acid by means of radical polymerization of acrylic acid and optional water-soluble, monoethylene unsaturated comonomers in an aqueous medium in the presence of at least one water-soluble initiator and at least one water-soluble regulator, wherein the polymerization is performed by means of a continuous process, and wherein low-molecular components are at least partially separated out of the aqueous polymer solution obtained after polymerization. Microstructured mixers and reactors are preferably used for the polymerization. At least one reactor and/or mixer having microstructures are preferably used for the process.
The document DE 102 45 858 A1 describes the use of water-soluble or water-dispersible, film building graft polymers which are obtainable by a radical polymerization of a vinyl ester of an aliphatic C1 to C24 carbonic acid in the presence of polyether with the mean molecular weight of at least 300 g/mol.
The document WO 2009/133186 A1 relates to a method for the continuous production of a polymer by radical polymerization, wherein at least three materials are mixed with microstructures in one or more mixers and are then polymerized in at least one reaction zone.
The document DE 198 14 739 A1 describes the use of polyalkylene oxide based graft polymers as solubilizers. The graft polymers are obtainable by grafting of    a) polyalkylene oxide with    b) at least one monomer, selected from the group            b1) C1-C30-alkylesters of monoethylenic unsaturated C3-C8-carboxylic acids;        b2) vinyl esters of aliphatic C1-C30-carboxylic acids;        b3) C1-C30-alkylvinylethers;        b4) N—C1-C12-alkyl-substituted amides of monoethylenic unsaturated C3-C8-carboxylic acids        b5) N,N—C1-C12-dialkyl substituted amides of monoethylenic unsaturated C3-C8-carboxylic acids as solubilizers.        
The document WO 2007/138053 A1 describes novel amphiphilic graft polymers based on water-soluble polyalkylene oxides (A) as a graft base and side chains formed by polymerization of a vinyl ester component (B), said polymers having an average of ≦1 graft site per 50 alkylene oxide units and mean molar masses Mw of from 3,000 to 100,000 g/mol. The inventive process describes the semi-batch process whereby the used reactor is preferably a stirred tank.
Processes for the preparation of graft polymers based on polyalkylene oxides are limited by their process parameters, since heat removal represents a considerable safety aspect. For this reason, longer reaction times are required, e.g., usually several hours. Amphiphilic graft polymers obtained in semi-batch processes, which are characterized by limited process parameters, are restricted in the structure variations. As a result, the nature of semi-batch-made graft polymers is that their polarity distributions are relatively narrow.
It would be desirable to produce a detergent composition containing an amphiphilic graft polymer having a broader polarity distribution. Graft polymers having broad polarity distributions provide a broader variety of cleaning benefits by treating and/or suspending a broader spectrum of soils. Graft polymers having narrow polarity distributions provide more limited cleaning benefits.